air and then
placed under pressure.

Fresh spots of oil or grease may sometimes be removed by impalpable
powders of some clay-like nature, absorbent and slightly alkaline.

A spot of ordinary black ink upon morocco, sheepskin, calf or smooth
parchment, loses its color when touched with a few drops of sorrel salt or
oxalic acid; but I will repeat here the advice already given that these
substances may alter certain colors and that it is best to first try them
on extra pieces of leather. If the tint lightens or changes only slightly,
the spot can be retoned and brightened simply with properly mixed
water-colors, after having neutralized, with an alkali, the traces of the
acid.

The yellowish spot which remains after the black ink has disappeared is
not very noticeable upon brown or yellowish skins, but on vellum or
parchment it is more or less apparent. How can this be removed? For if one
is obliged to prolong the action of the oxalic acid on the iron oxide
which causes it, this portion of the skin not only loses its gloss, but
also becomes subject to a more or less rapid process of dissolution.[10]

When the spots are of Chinese ink, old or recent, and have sunk into the
texture, as sometimes happens, they resist all known agents.

Most of the old bindings which have been long exposed for sale on the
parapets of our quays, have been at one moment roasted by an ardent sun
and at the next distended by a damp atmosphere; they have, therefore,
contracted "skin troubles" more or less curable according to the duration
of their ordeal. The gentler regimen of the bookshelves, placed in a room
where the temperature is more nearly uniform, sometimes suffices to
restore their warped covers; but when the surface of the leather has
fallen off in scales, carrying away the gold tooling, it is better, if
they are worthy of it, to deliver them to the binder for new covers; that
is, of course, when the paper, the essential organ of their existence, is
not musty beyond recovery. If the paper is in bad shape, the book is lost
or, at least, is beyond giving pleasure to a bibliophile; it resembles a
very old man attacked by an incurable disease; it is useful only for
reference.

Some books, placed in less rude conditions, have only the skin stripped
here and there by contact with rougher neighbors trimmed with nails or
clasps, with hard boards or with wicker-work, but movement against these
objects might ruin an entire library in a sin